The present invention relates to an ultrasound diagnostic system, and more particularly, to a method and apparatus for observing a biopsy needle and guiding the same towards a target object within the human body in a three-dimensional ultrasound diagnostic system that uses interventional ultrasound system.
In the field of interventional ultrasound imaging, a medical procedure is performed which, for diagnostic or treatment purposes, takes a sample of a target object, for example, the tissue of a specific internal organ of the patient""s body by inserting a medical device such as a biopsy needle into the patient""s body and, at the same time, monitoring the movement of such medical device within the patient""s body in real time with the use of the ultrasound diagnostic system. Thus, in order to ensure reliable diagnosis, it is necessary to display an ultrasound image in such manner that a positional relationship between the target object and the biopsy needle can precisely be identified.
However, since a conventional two-dimensional ultrasound diagnostic system displays the biopsy needle in a plane defined by the axial and lateral directions of the transducer, it is difficult to precisely identify the location of the biopsy needle in the displayed ultrasound image when a movement in elevation of the biopsy needle occurs. A similar problem arises for the two-dimensional ultrasound diagnostic system which can generate a two-dimensional B-mode image of human organs and can show the guide line of the biopsy needle on the image being displayed by using a geometrically adequate biopsy guide. More specifically, since the transducer used in the two-dimensional ultrasound diagnostic system has to perform beam-focusing in the direction of elevation as well, it is not viable to display the movement in elevation of the biopsy needle in a two-dimensional image when the biopsy needle is not located in a plane defined by the axial and lateral directions, i.e., when the movement of the biopsy needle is to the direction of elevation. The difficulty in observing a target object in the displayed ultrasound image is attributed mainly to the fact that most of the target objects take a form of a three-dimensional sphere, while the two-dimensional ultrasound diagnostic system displays only a sectional view of the portion where the transducer is currently located. Therefore, visualization capabilities of a target object to be subject to a tissue inspection are inevitably restricted by the inherent characteristics of the two-dimensional ultrasound diagnostic system.
In an attempt to circumvent the above problems, a three-dimensional ultrasound diagnostic system is often used when performing a medical inspection, where a biopsy needle is used, due to the fact that a positional relationship between the biopsy needle and the target object can clearly be observed in a volume image provided by the three-dimensional ultrasound diagnostic system. Among the several methods for observing the biopsy needle adopted for the three-dimensional ultrasound diagnostic system, the following two methods are known as being most widely used. The first is a method wherein the biopsy guide is attached to the transducer as in a conventional two-dimensional diagnostic system, and the biopsy needle is displayed by using known information on a geometrical structure of the biopsy needle; and the other is a method called xe2x80x9ca free-hand style method.xe2x80x9d In the free-hand style method, the location of the biopsy needle is discerned by the user""s estimation or sensation wherein the user holds a three-dimensional transducer with one hand as shown in FIG. 1, and manipulates the biopsy needle with the other hand without using the biopsy guide.
As described above, the three-dimensional ultrasound diagnostic system can also provide a guide line as is provided by a two-dimensional ultrasound diagnostic system, in case that the biopsy guide is used. However, in a display image showing a volume rendered with respect to x, y and z axes, the biopsy needle is typically displayed on one of the three planes defined by the x, y and z axes. Thus, unless the three-dimensional ultrasound image is rearranged, it is difficult to precisely observe the movement of the biopsy needle since the biopsy needle is indicated merely as a point in the rendered image. The free-hand style method cannot display a location of the biopsy needle precisely. Further, for the free-hand style method, diagnosis is performed mainly by estimation or sensation of the user so that the accuracy of diagnosis depends on the skill of the user.
It is accordingly an object of the present invention to provide a method and apparatus for accentuating a relationship between a biopsy needle and a target object by contouring the biopsy needle in a three-dimensional ultrasound image provided by a three-dimensional ultrasound diagnostic system.
It is another object of the present invention to provide a method and apparatus for automatically guiding a biopsy needle into the human body by automatically extracting a target object from a three-dimensional ultrasound image, contouring the target object, and obtaining information on locations of and a relationship between the extracted target object and the biopsy needle being guided.
In accordance with one aspect of the present invention, an apparatus for enabling a biopsy needle to be observed in a three-dimensional ultrasound image is provided which comprises means for transmitting ultrasound signals towards a target object and receiving echo signals reflected from the target object; means for forming a three-dimensional volume image by receiving and combining two-dimensional data from the transmitting means; means for extracting the target object from the three-dimensional volume image; means for estimating a location of the extracted target object and a location of the biopsy needle that is inserted into the extracted target object; means for displaying the extracted target object; and means for calculating an error in location between the biopsy needle and the extracted target object based on the estimation and providing the calculated error to the estimating means.
In accordance with another aspect of the present invention, a method of enabling a biopsy needle to be observed in a three-dimensional ultrasound image is provided which comprises the steps of acquiring a two-dimensional ultrasound image of a subject; generating a three-dimensional volume image based on the two-dimensional ultrasound image; segmenting a target image, which corresponds to a target object within the subject, from the three-dimensional volume image; displaying a guide line of the biopsy guide on the segmented target image; extracting the segmented target image; acquiring information on a location of the biopsy needle by reference to the segmented target image; calculating an error based on the information; and displaying a guiding status of the biopsy needle based on the calculated error.